I agree with above. It is probably a huge paging file (it's happened), and/or hibernation file (do you have a lot of RAM?) Both are hidden system files in the root of the system drive. Or shadow copies or restore points.

The two partitions you are seeing..... are you sure the one "system reserved" is 100GB? 100mb is typical.

Tagging for the lulz. Well, and to see if there's another OMGHUGE Win8 swapfile.

Well, stick around. But you may not be laughing at what you think you are laughing at ("inconceivable!")

You'll be laughing at me.I didn't mention it because I figured someone would dig up my old posts, but I am a... I hate the word newb.... let's say I'm a dabbler, not an expert at anything.Built the computer in August. I was probably the one who mistakenly set up the giant 100GB partition. I don't remember doing it, but I'm pretty sure Windows had nothing to do with it, lol. An yes, it's "GB". Too late to reset?

Is it even possible for the end-user to configure the size of the partition that Windows uses to store the WinRE (I believe that's what it's for)? I've never seen it any size other than 100MB and don't recall ever being given the opportunity to size that partition during setup.

It's a good idea with W8. It uses it for the enhanced shutdown/startup.

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Too late to reset?

Not really, but it'll be kinda difficult. It's large enough that you should be able to clone your current system to the 100 GB partition. Once you do that, then you can delete your current partition and expand into the newly available space. Do your homework first, and have a backup.

It's a good idea with W8. It uses it for the enhanced shutdown/startup.

Aren't those two separate things? The Hibernate file allows you to offload your entire session to disk - usually somewhere in the size of 2-5GB - possibly more depending on what you're doing. While the new enhanced shutdown/startup in Windows 8 does use a hiberfile, it doesn't store your entire session; not even close.

It's a good idea with W8. It uses it for the enhanced shutdown/startup.

Aren't those two separate things? The Hibernate file allows you to offload your entire session to disk - usually somewhere in the size of 2-5GB - possibly more depending on what you're doing. While the new enhanced shutdown/startup in Windows 8 does use a hiberfile, it doesn't store your entire session; not even close.

What difference does it make whether the hiberfil.sys file keeps your session or not? It is necessary to have one for enhanced shutdown/startup to work. So the original question "Is a hibernate file necessary" is aptly answered. Yes it is needed for certain functions to work.

It's a good idea with W8. It uses it for the enhanced shutdown/startup.

Aren't those two separate things? The Hibernate file allows you to offload your entire session to disk - usually somewhere in the size of 2-5GB - possibly more depending on what you're doing. While the new enhanced shutdown/startup in Windows 8 does use a hiberfile, it doesn't store your entire session; not even close.

What difference does it make whether the hiberfil.sys file keeps your session or not? It is necessary to have one for enhanced shutdown/startup to work. So the original question "Is a hibernate file necessary" is aptly answered. Yes it is needed for certain functions to work.

I was asking if they were two different files, because they serve two different functions. If you disable "Hibernation" in Windows 8, you don't disable your ability to use the enhanced shutdown/startup. So that would imply that the Hiberfile and the Hibernation file are two separate things, no?

How are you doing that: through the Power Options in the control panel or by running "powercfg -h off" from an administrative command prompt?

The first will simply prevent Win 8 from hibernating automatically via timeout. The second should disable the hibernation feature throughout the entire OS and remove the hiberfile altogether. This will also break/disable any other functionality that requires hibernation, like enhanced shutdown/startup.

How are you doing that: through the Power Options in the control panel or by running "powercfg -h off" from an administrative command prompt?

The first will simply prevent Win 8 from hibernating automatically via timeout. The second should disable the hibernation feature throughout the entire OS and remove the hiberfile altogether. This will also break/disable any other functionality that requires hibernation, like enhanced shutdown/startup.

I didn't do anything myself manually - when I upgraded from Windows 7 Ultimate to Windows 8 Pro on my desktop; Hibernation was already automatically disabled under the shut-down and power options menu.